Re: Sending signed values problem

If you send a value between 0 and -128 you get a one byte value.  If you
send a value between -129 and -32768 you get a two byte value.  This is BER
encoding.

You showed -130 being encoded properly, which is between -128 and -256
which is what you say doesn't work.  I don't understand why you say both of
those things.

  Bill


On Wed, Jun 28, 2017 at 3:05 AM, <[email protected]> wrote:

> The problem is that the OID is a 16bit Integer, if i send -256 i get a
> 2byte signed value, but if i send any value between 0 and -128 i get a
> 1byte signed value, thus losing the range from -128 to -256, same thing for
> the positive range.
>
> I'm sorry, in the last mail i gave the wrong example reporting -130.
>
> Il 27 giugno 2017 alle 18.35 Bill Fenner <[email protected]> ha scritto:
>
> On Tue, Jun 27, 2017 at 11:37 AM, <[email protected]> wrote:
>
> Thank you so much for the reply, the command i'm using is the following:
>
> snmpset -v 2c -c public "IP" "OID" = -100
>
> Watching the data over wireshark tho, the data length for that command is
> 1.
>
> But if i send for example -130 i get a data length of 2.
>
> Yes, that is correct behavior.  What is the problem?
>
>   Bill
>
>
> Il 27 giugno 2017 alle 16.51 Bill Fenner <[email protected]> ha scritto:
>
> On Thu, Jun 22, 2017 at 10:37 AM, corvace.fabrizio--- via Net-snmp-users <
> [email protected]> wrote:
>
> Hello,
>
> I'm currently struggling with a data problem.
>
> I have a system where i have to SET a value, the value is of type Integer
> (-32768.32767).
>
> When sending a value over 255 i have no problem with sign, if i scan with
> wireshark i see a transmission of ASN type 2(Integer) with 2 bytes of data,
> and the data is correctly sent with sign.
>
> But whenever i try to send a value that is less that 256, therefore fits
> in a byte, the transmission is still of type 2, but it sends out one single
> byte of data, thus cutting out the range from -129 to -255 and from +128 to
> +255.
>
> I would have thought that since the OID is of type Integer (explicitly
> 16bit) the data would still have been sent as 2bytes.
>
> BER encoding is variable length, no matter what the restrictions on the
> range of the integer - restrictions like that are managed at a higher layer.
>
> As you surmise, the BER encoding of values from -129 to -255 and +128 to
> +255 are two bytes long.
>
> I tried looking for a way of forcing 2 byte data send, but with no luck.
> Am i missing something?
>
> How are you sending your data?  I do not know of a way to force net-snmp
> to behave in this incorrect way.
>
>   Bill
>
>
>

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